1. Field of the Invention
The present invention relates to an oscillator circuit which stably generates an oscillation signal of a predetermined frequency against a change in external voltage supply having a wide range, temperature, and a semiconductor process, and more particularly, to an oscillator circuit, and more particularly, to an oscillator circuit which compensates for external voltage supply having a wide range, temperature, and a semiconductor process capable of stably generating a constant oscillation signal against a change in temperature and a change in process while compensating for a change in a period signal according to voltage supply used for an integrated circuit device and a chip.
2. Description of the Related Art
An oscillator has been widely used to provide a timing signal of electronic devices including a computer, a system, or communication devices, or the like.
The oscillator circuit needs to compensate for external changes in three elements, that is, external voltage supply, temperature, and a process for an oscillator to stably output an oscillation signal.
However, there are problems in that the oscillator in accordance with the related art compensates for only the change in temperature among the three elements to output the oscillation signal that is not precision and does not completely compensate for the change in temperature when the voltage supply and the process are changed.
FIG. 1 illustrates a general oscillator circuit in accordance with the related art.
Referring to FIG. 1, a general oscillator circuit 100 in accordance with the related art is configured to include a resistive element 110, a capacitor 120, a comparator 130, an output pulse generator 140, and a reset circuit 150.
Current I is generated by the resistive element 110 and flows from a power supply source VDD toward a capacitor 120.
The comparator 130 has a first connection end of a connection node N1 that connects the resistive element 110 to the capacitor 120, a second input end that receives reference voltage VREF, and an output end that is connected to the output pulse generator 140.
The output pulse generator 140 outputs the oscillation signal and provides a reset signal for controlling a discharge of the capacitor 120 to the reset circuit 150. The output pulse generator 140 repeatedly performs a charge and discharge of the capacitor 120, such that the oscillator 120 periodically generates the oscillation signal.
However, the general oscillator circuit 100 in accordance with the related art has the following problems.
That is, since the current I is changed according to the voltage supply VDD and a resistance value of the resistive element 110 is changed according to the change in temperature, the current I is consecutively changed. As a result, the oscillator circuit 100 may change the output oscillation signal frequency according to the change in voltage supply VDD and the change in temperature.
FIG. 2 illustrates another oscillator circuit which compensates for temperature in accordance with the related art.
Referring to FIG. 2, an oscillator circuit 200 which compensates for temperature in accordance with the related art is configured to include first and second transistors 211 and 212 that configures a current mirror type circuit 210, a third transistor 220 that controls an amount of first current I1 output from the current mirror type circuit 210 by control voltage Vg, a resistive element 230 that generates second current I2, a capacitor 240 that receives third current I3 that is a sum of the first current I1 and the second current I2, a comparator 250, a reset circuit 260, and an output pulse generator 270.
The capacitor 240 is charged by receiving the third current I3 and the output pulse generator 270 activates the reset circuit 260 to discharge the capacitor 240. The repeated charge and discharge of the capacitor 240 periodically generates the pulse oscillation signal.
However, the oscillator circuit 200 which compensates for temperature in accordance with the related art has also the following problems.
That is, when the external voltage supply and the process are not changed, the supplied third current I3 is constant against the change in temperature. However, when the external voltage supply and the process are changed, there are problems in that the current supply I3 is changed according to the change in temperature and thus, the oscillation signal may not be constantly output.
In addition, there is a problem in that the output oscillation signal frequency are changed according to the change in characteristics of external voltage supply and temperature of the oscillator even though current is supplied thereto, independent of the change in external voltage supply and temperature.